1. Field of Use
This invention relates to fabricating composite pressure vessels such as rocket motor cases that have a metal or resin and filament shell lined with elastomer. This invention, more specifically, relates to a method of fabricating these elastomer lined vessels where a tacky ribbon comprising cured or curable elastomer is used in providing the liner.
2. Prior Art
The elastomeric liner used in rocket motor case performs two major functions. First, it thermally insulates the propellant from the case; second, it seals the case from leakage of propellant gases. Prior art methods of insulator manufacture include (1) the molding of green rubber stock in matched metal dies and (2) the hand layup of green rubber sheets followed by vulcanization and grinding to final dimensions. In either circumstance, insulators are next positioned on case winding mandrels (or alternately within a preformed case) where various splicing, hand buffing, bonding and shrinking operations are performed. These methods of fabrication are disadvantageous in view of the need for: a) large facility investments, b) extensive precision tooling, c) long lead times for production that give rise to an inability to accommodate design changes quickly and cheaply, d) failure modes such as insulator to case unbonding being introduced because of hand and bonding operations, and e) labor intensive unit costs.
U.S. Pat. No. 3,303,079 relates to preparation of elastomer lined rocket motor cases. This patent proposes laying calendared sheets of rubber on a mandrel to produce an elastomer precursor layer to the liner. The elastomer layer is encased in a resin and filament wound shell and the resin and elastomer cured together in providing the elastomer lined composite vessel. Laying calendared sheets manually about a mandrel, however, is labor intensive; and it is especially difficult when building thickness with more than two sheets of the elastomer and when covering contoured portions of the mandrel with precise, but variable thicknesses.